在Scala中创建星期枚举的简明方法

Question

我是Scala的新手,所以请好好的.如果我遗漏了一些明显的东西,你不得不原谅我.

我正在尝试创建一个类似枚举的结构来表示Scala中一周的日子.我想要一个方法,接受一个字符串,可以是数字1到7,当天的全名,或三个字母的缩写,任何大小写,并返回正确的一天.理想情况下,我希望能够通过写作来检索正确的日子DayOfWeek(_),据我所知,事情意味着这种方法需要apply.单个值也必须是一个被调用的特征的子类(或混合),目前这个特征CalendarField不定义任何方法或成员.

这是我目前的尝试:

object DayOfWeek extends Enumeration with CalendarField {

    val Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday = Value

    def apply(v:String) = {
        v.toUpperCase match {
            case Int(x) => x match {
                case 1 => Sunday
                case 2 => Monday
                case 3 => Tuesday
                case 4 => Wednesday
                case 5 => Thursday                  
                case 6 => Friday
                case 7 => Saturday
                case _ => throw new IllegalArgumentException("Invalid value for day of week: " + v)
            }
            case "SUN" | "SUNDAY" => Sunday
            case "MON" | "MONDAY" => Monday
            case "TUE" | "TUEDAY" => Tuesday
            case "WED" | "WEDNESDAY" => Wednesday
            case "THU" | "THURSDAY" => Thursday
            case "FRI" | "FRIDAY" => Friday
            case "SAT" | "SATURDAY" => Saturday
            case _ => throw new IllegalArgumentException("Invalid value for day of week: " + v)
        }
    }
}

object Int {
    def unapply(s : String) : Option[Int] = try {
        Some(s.toInt)
    } catch {
        case _ : java.lang.NumberFormatException => None
    }
}

这失败了几点:

1. 单个值不是子类CalendarField- 它们只是Values.
2. 我已经定义了一个apply方法但是DayOfWeek(_)没有用 - 我(模糊)猜测这是因为它期望调用一个构造函数并且DayOfWeek是一个对象,而不是一个类？或者是因为Enumeration(s:String)已被使用？这有什么方法吗？

任何关于如何解决这些问题或更简洁的解决方案的建议都将不胜感激.谢谢.

Answer 1

我可能会实现这样的事情:

sealed trait DayOfWeek
case object Monday extends DayOfWeek
case object Tuesday extends DayOfWeek
// etc.

object DayOfWeek {
   def unapply(s: String): Option[DayOfWeek] = s.toUpperCase match {
      case Int(x) => x match {
         case 1 => Some(Sunday)
         // ...
         case _ => None
      }
      case "SUN" | "SUNDAY" => Some(Sunday)
      // ...
      case _ => None
   }

   def apply(s: String): DayOfWeek = s match {
      case DayOfWeek(d) => d
      case _ => throw new IllegalArgumentException(
                   "Invalid value for day of week: " + s)
   }

}